Liquid crystal display panel and fabricating method thereof

ABSTRACT

A liquid crystal display (LCD) panel and a fabricating method thereof are described. First, a first substrate and a second substrate are provided. A liquid crystal monomer layer is then formed on the surface of at least one of the first and second substrates. Next, a curing step is performed to the liquid crystal monomer layer to induce a polymerization reaction, so as to form a liquid crystal polymer layer. Thereafter, the first and second substrates are assembled and a liquid crystal layer is filled between the first and second substrates.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 95133022, filed on Sep. 7, 2006. All disclosure of the Taiwanapplication is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display panel and a fabricatingmethod thereof. More particularly, the present invention relates to aliquid crystal display (LCD) panel and a fabricating method thereof,wherein the problem of insufficient anchoring energy of an alignmentsurface in the LCD panel is resolved and the performances of the LCDpanel in surface gliding and voltage-transmittance (V-T) curve shift areimproved, so that the photo-electronic properties of a LCD is improved.

2. Description of Related Art

Along with the great advancement of computer performance and the rapiddevelopment of the Internet and multimedia technology, the volume ofvideo or image apparatus is getting smaller and lighter. In thedevelopment of displays, liquid crystal displays (LCD) having suchadvantages as high image quality, high space efficiency, low powerconsumption, and no radiation have become the major products in displaymarket along with the advancement of photo-electronic techniques andsemiconductor fabricating techniques.

A LCD includes a backlight module and a LCD panel, and a conventionalLCD panel is composed of two substrates and a liquid crystal layerfilled between the two substrates. Generally, during the manufacturingprocedure of a LCD panel, alignment films are disposed on both thesubstrates so that liquid crystal molecules can be arranged in aparticular arrangement. A conventional method of forming an alignmentlayer is to perform an alignment process to an alignment material afterthe alignment material is coated over a substrate. The alignment processis categorized into contact alignment and non-contact alignment. Eventhe problems such as static produced by contact rubbing alignment andparticle contamination can be resolved by non-contact alignment process,the problem of insufficient anchoring energy of the alignment surfacemay be caused therein. Insufficient anchoring energy of an alignmentsurface may result in bad display quality of the LCD panel.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to provide a liquidcrystal display (LCD) panel and a fabricating method thereof, whereinthe LCD panel has stronger anchoring energy and better performance insurface gliding and voltage-transmittance (V-T) curve shift,accordingly, the photo-electronic properties of the LCD are improved,for example, imaging sticking is reduced.

The present invention provides a LCD panel. The LCD panel includes afirst substrate and a second substrate, at least one liquid crystalpolymer layer disposed on the surface of at least one of the first andthe second substrate, and a liquid crystal layer disposed between thefirst and the second substrate.

The present invention provides a fabricating method of a LCD panel.According to the method, a first substrate and a second substrate areprovided, and then a liquid crystal monomer layer is formed on thesurface of at least one of the first and the second substrate. Next, acuring step is performed to the liquid crystal monomer layer to induce apolymerization reaction and so as to form a liquid crystal polymerlayer. After that, the first and the second substrate are assembledtogether and a liquid crystal layer is filled between the first and thesecond substrate.

According to the present invention, the anchoring energy of a LCD panelcan be increased through a liquid crystal polymer layer. Besides, aliquid crystal polymer layer may also be formed on a film which has beenperformed with an alignment process to serve as an alignment assistantlayer and so as to improve the alignment properties of liquid crystalmolecules and to resolve the problem of insufficient anchoring energyafter alignment. Accordingly, surface gliding and V-T curve shift can bereduced and the display quality of the LCD panel can be improved, forexample, imaging sticking can be reduced.

In order to make the aforementioned and other objects, features andadvantages of the present invention comprehensible, a preferredembodiment accompanied with figures is described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a fartherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIGS. 1A˜1E are cross-sectional views illustrating the fabricating flowof a liquid crystal display (LCD) panel according to the firstembodiment of the present invention.

FIGS. 2A˜2E are cross-sectional views illustrating the fabricating flowof a LCD panel according to the second embodiment of the presentinvention.

FIG. 3 is a picture showing that serious surface gliding may be observedat the IPS electrode region when the surfaces of the first and thesecond substrate without liquid crystal polymer layer are aged throughheating and voltage supply.

FIG. 4 is a picture showing that no surface gliding is observed at theIPS electrode region when the surfaces of the first and the secondsubstrate with liquid crystal polymer layer are aged through heating andvoltage supply.

FIG. 5 is a graph showing the surfaces of the first and the secondsubstrate have serious V-T curve shift when no liquid crystal polymerlayer is formed thereon.

FIG. 6 is a graph showing the surfaces of the first and the secondsubstrate have very slight V-T curve shift when liquid crystal polymerlayers are formed respectively on the surfaces of the first and thesecond substrate.

DESCRIPTION OF EMBODIMENTS First Embodiment

FIGS. 1A˜1E are cross-sectional views illustrating the fabricating flowof a liquid crystal display (LCD) panel according to the firstembodiment of the present invention. Referring to FIG. 1A, the firstsubstrate 101 is composed of the substrate 100 and a film layer 102formed on the substrate 100, and the second substrate 201 is composed ofthe substrate 200 and a film layer 202 formed on the substrate 200. Thesubstrates 100 and 200 may be glass substrates, silicon substrates,flexible plastic substrates, or any existing substrate which can be usedfor fabricating display panel. If the display panel in the presentinvention is a passive matrix display panel, then film layer 102 andfilm layer 202 may be respectively an electrode layer. If the displaypanel in the present invention is an active matrix display panel, thenfilm layer 102 may be an active matrix device layer, and film layer 202may be a common electrode layer. The material of the electrode layer maybe organic conductive material, such as poly (3,4-ethylenedioxythiophene) (PEDOT), or inorganic conductive material, such asindium tin oxide (ITO) or indium zinc oxide (IZO). According to otherembodiments of the present invention, besides the conductive layersdescribed above (electrode layer or active matrix device layer), thesurface layers of film layer 102 and film layer 202 may also be aninsulating layer, wherein an insulating layer may be further coated overthe electrode layer or the active matrix device layer, and theinsulating layer may be a passivation layer, a overcoat layer, or aplanarization layer. The material of the insulating layer may be organicinsulating material, such as organic resin or color filer layer, orinorganic insulating material, such as SiO_(x) or SiN_(x). Therefore,the first substrate 101 may be an active device array substrate or apassive matrix substrate, and the second substrate 201 may be a colorfilter substrate or a counter electrode substrate.

Referring to FIG. 1B, alignment processes 104 and 204 are respectivelyperformed to the surfaces of the first substrate 101 and the secondsubstrate 201. The alignment processes 104 and 204 may be particle beamalignment processes, photo alignment processes, or contact alignmentprocesses. In an embodiment, the particle beam alignment process may bean ion beam alignment process, an electron beam alignment process, aplasma alignment process, or an oblique evaporation alignment process.Namely, non-contact alignments are performed to the surfaces of thefirst substrate 101 and the second substrate 201 by using ion beam,electron beam, plasma, or oblique evaporation. In addition, the contactalignment process may be a rubbing alignment process, nano imprintingalignment process, or an atomic force microscopy probe contact alignmentprocess. Moreover, photo alignment process may be a photo-polymerizationalignment process, a photo-decomposition alignment process, or aphoto-isomerization alignment process. The foregoing photo alignmentprocess is a non-contact alignment process, wherein the surfaces of thefirst substrate 101 and the second substrate 201 are illuminated toinduce polymerization reaction, decomposition reaction, or isomerizationreaction. The isomerization reaction refers to transformation fromtrans-structure to cis-structure or from cis-structure totrans-structure.

According to another embodiment of the present invention, the alignmentprocesses 104 and 204 may be multi-domain alignment processes, namely, amulti-domain alignment process is performed to the surfaces of the firstsubstrate 101 and the second substrate 201. Thus, different areas on thesurfaces of the first substrate 101 and the second substrate 201 havedifferent alignment directions. Moreover, the multi-domain alignmentprocess may be performed along with at least one of the particle beamalignment process, the photo alignment process and the contact alignmentprocess to accomplish the purpose of multi-domain alignment.

Then referring to FIG. 1C, liquid crystal monomer layers 106 and 206 areformed respectively on the surfaces of the aligned first substrate 101and second substrate 201. The method for forming liquid crystal monomerlayers 106 and 206 on the surface of the first substrate 101 and thesecond substrate 201 may be spin coating, slot die coating, screenprinting, evaporation, relief printing, inkjet printing, or any coatingmethod. In addition, the liquid crystal monomer layers 106 and 206 maybe homogeneous type liquid crystal monomers, homeotropic type liquidcrystal monomers, or mixed type monomers. The liquid crystal monomerlayers 106 and 206 may also be multi-layer liquid crystal monomerscomposed of at least one of homogeneous type liquid crystal monomers,homeotropic type liquid crystal monomers, or mixed type monomers. In anembodiment of the present invention, a homogeneous type liquid crystalmonomer may be a compound as shown in chemical formula (1), which may bereferred to U.S. Pat. No. 6,597,422.

After that, curing steps 108 and 208 are performed to the liquid crystalmonomer layers 106 and 206 in FIG. 1C to induce polymerization reactionsin the liquid crystal monomer layers 106 and 206, so as to form liquidcrystal polymer layers 106a and 206 a, as illustrated in FIG. 1D. In anexemplary embodiment, the foregoing curing steps 108 and 208 may beilluminating steps (such as UV exposure) or heating steps. Next,referring to FIG. 1E, the first substrate 101 and the second substrate201 are assembled together and a liquid crystal layer 150 is filledbetween the first substrate 101 and the second substrate 201.

In the present embodiment, besides performing alignment processes to thesurfaces of the first substrate 101 and the second substrate 201, liquidcrystal polymer layers 106 a and 206 a are further formed on thesurfaces of the aligned first substrate 101 and second substrate 201,wherein the liquid crystal polymer layers 106 a and 206 a may be servedas alignment assistant layers to resolve the problem of insufficientanchoring energy produced by conventional non-contact alignment process,and further to improve the display quality of the LCD panel.

In the embodiment described above, alignment processes are performed onboth substrates and liquid crystal polymer layers are formed on bothsubstrates, however, the present invention is not limited thereto,instead, it could be only one substrate that is performed with analignment process and formed with a liquid crystal polymer layerthereon.

Moreover, according to the present invention, liquid crystal polymerlayers may also be formed directly on the surfaces of the firstsubstrate 101 and the second substrate 201 without performing alignmentprocess additional, namely, the step in FIG. 1B is skipped after thestep illustrated in FIG. 1A, instead, the step of coating the liquidcrystal monomer layers 106 and 206 illustrated in FIG. 1C is performeddirectly, and the curing steps 108 and 208 are performed to form theliquid crystal polymer layers 106 a and 206 a as shown in FIG. 1D. Sincealignment process does not have to be performed to a typical verticalalignment LCD panel, the method for improving display quality of a LCDpanel by using liquid crystal polymer layers provided by the presentinvention may also be applied to a vertical alignment LCD panel whichdoes not require alignment processing.

The method of the present invention may also be applied to existing LCDpanels which need alignment material, and such application will bedescribed in detail in the second embodiment.

Second Embodiment

FIGS. 2A-2E are cross-sectional views illustrating the fabricating flowof a LCD panel according to the second embodiment of the presentinvention. Referring to FIG. 2A, a first substrate 101 and a secondsubstrate 201 are provided first. The composition and material of thefirst substrate 101 and the second substrate 201 are as those describedin the first embodiment, therefore will not be described herein. Next, afirst alignment material layer 120 and a second alignment material layer220 are respectively formed on the surfaces of the first substrate 101and the second substrate 201. The first and the second alignmentmaterial layers 120 and 220 may be an organic alignment material or aninorganic alignment material. In an embodiment, the organic alignmentmaterial includes poly vinyl alcohol, polyimide, polyamic acid,azo-benzene, poly vinyl cinnamate, compound containing coumarin group,compound containing chalcone group, or other existing organic alignmentmaterial. In another embodiment, the inorganic alignment materialincludes diamond-like carbon, SiOX, SiNe, or other existing inorganicalignment material.

Then referring to FIG. 2B, alignment processes 122 and 222 arerespectively performed to the first and the second alignment materiallayers 120 and 220. In an embodiment, the alignment processes 122 and222 may be particle beam alignment processes, photo alignment processes,or contact alignment processes. In an embodiment, the foregoing particlebeam alignment process may be an ion beam alignment process, an electronbeam alignment process, a plasma alignment process, or an obliqueevaporation alignment process. The contact alignment process may be arubbing alignment process, a nano imprinting alignment process, or anatomic force microscopy probe contact alignment process. The photoalignment process may be a photo-polymerization alignment process, aphoto-decomposition alignment process, or a photo-isomerizationalignment process. Similarly, the foregoing alignment processes 122 and222 may also be multi-domain alignment processes described above.

Next, referring to FIG. 2C, liquid crystal monomer layers 106 and 206are formed on the aligned first and second alignment material layers 120and 220. The material of the liquid crystal monomer layers 106 and 206is the same or similar to that in the first embodiment. After that,curing steps 108 and 208 are performed to the liquid crystal monomerlayers 106 and 206 in FIG. 2C to induce polymerization reactions on theliquid crystal monomer layers 106 and 206, so as to form liquid crystallo polymer layers 106 a and 206a, as illustrated in FIG. 2D. In anexemplary embodiment, the curing steps 108 and 208 may be illuminatingsteps (such as UV exposure) or heating steps. After that, referring toFIG. 2E, the first substrate 101 and the second substrate 201 areassembled together and a liquid crystal layer 150 is filled between thefirst substrate 101 and the second substrate 201.

In the present embodiment, besides performing alignment processes to thefirst and the second alignment materials, liquid crystal polymer layers106 a and 206 a are further formed on the aligned first and secondalignment material layers, wherein the liquid crystal polymer layers 106a and 206 a may be used as alignment assistant layers for resolving theproblem of insufficient anchoring energy caused when conventionalnon-contact alignment processes are used, and further to improve thedisplay quality of the LCD panel.

Moreover, in the embodiment described above, alignment processes areperformed to the alignment material layers of both substrates and liquidcrystal polymer layers are formed on both substrates, however, thepresent invention is not limited thereto, instead, it could also be thatonly one of the two substrates is performed with an alignment processand formed with a liquid crystal polymer layer thereon.

In the embodiment described above, alignment material layers are formedon the two substrates and alignment processes are performed to thealignment material layers, however, according to the present invention,liquid crystal polymer layers may also be formed directly on thealignment material layers without performing alignment process. Namely,the step in FIG. 2B is skipped after the step illustrated in FIG. 2A,and the step of coating the liquid crystal monomer layers 106 and 206illustrated in FIG. 2C are performed directly, and the curing steps 108and 208 are performed to form the liquid crystal polymer layers 106 aand 206 a as shown in FIG. 2D. Since alignment process does not have tobe performed to a typical vertical alignment LCD panel, the method forimproving display quality of a LCD panel by using liquid crystal polymerlayers provided by the present invention may also be applied to avertical alignment LCD panel which does not requirement alignmentprocessing.

Several examples will be described below to show that the method ofusing liquid crystal polymer layers as alignment assistant layers in thepresent invention can improve the display quality of a LCD panel,however, these examples are not for limiting the present invention.Referring to table 1, the alignment material RD-100 is manufactured byELSICON company, the alignment material PIA-5310-06C is manufactured byCHISSO company, and the alignment materials SE-7492 and RN-1349 aremanufactured by NISSAN company. Besides, liquid crystal polymer layersare formed in the LCD panel to serve as alignment assistant layers inexamples 1˜5, while no liquid crystal polymer layers is used asalignment assistant layer in the comparative examples 1˜5. “OK’ insurface gliding test represents that the alignment surface has anchoringenergy of acceptable quality, while “X” represents that the anchoringenergy of the alignment surface is insufficient. The testing method andtheory can be referred to the document (LCT3-3) published by T. Suzukietc in IDW2005. Moreover, “OK” in V-T curve shift test represents thatthe LCD panel has stable photo-electronic properties, while “X”represents that the photo-electronic properties of the LCD panel are notgood.

TABLE 1 Alignment Alignment Liquid crystal Surface V-T material processpolymer layer gliding test curve shift test Example 1 RD-100Illuminating Yes OK OK Comparative RD-100 Illuminating No X X example 1Example 2 RN-1349 Illuminating Yes OK OK Comparative RN-1349Illuminating No X X example 2 Example 3 RD-100 Ion beam Yes OK OKComparative RD-100 Ion beam No X X example 3 Example 4 PIA-5310- Ionbeam Yes OK OK 06C Comparative PIA-5310- Ion beam No X X example 4 06CExample 5 SE-7492 Rubbing Yes OK OK Comparative SE-7492 Rubbing No OK OKexample 5

An example and a comparative example are further illustrated in table 2below to describe that the anchoring energy in a LCD panel can beimproved in the present invention by using liquid crystal polymer layersas alignment assistant layers. However, these examples are not intendedto limiting the present invention. As shown in table 2, the anchoringenergy in example 1 is obviously higher than that in comparative example1 because liquid crystal polymer layers are used as alignment assistantlayers.

TABLE 2 Anchoring Alignment Alignment Liquid crystal energy materialprocess polymer layer (J/m²) Example 1 RD-100 Illuminating Yes 9.17E−05Comparative RD-100 Illuminating No 1.37E−05 example 1

In addition, the surface gliding observed at the electrode region whenthe surfaces of the first and the second substrate without liquidcrystal polymer layer are aged through heating and voltage supply (topleft part of FIG. 3) and the surface gliding observed at the electroderegion when the surfaces of the first and the second substrate withliquid crystal polymer layers are aged through heating and voltagesupply (top left part in FIG. 4) are further illustrated. In FIG. 3,serious surface gliding can be observed, while in FIG. 4, no surfacegliding is observed.

Moreover, the situation of V-T curve shift when no liquid crystalpolymer layer is formed on the surfaces of the first and the secondsubstrate (as shown in FIG. 5), and the situation of V-T curve shiftwhen liquid crystal polymer layers are formed thereon (as shown in FIG.6) are illustrated. In FIG. 5, serious V-T curve shift can be observed,while in FIG. 6, there is only very slight V-T curve shift.

In overview, the present invention has following advantages:

-   -   1. In the present invention, liquid crystal polymer layers are        formed in a LCD panel to increase the anchoring energy of the        LCD panel and to improve the performance of the LCD panel in        surface gliding and V-T curve shift, so that the        photo-electronic properties of the LCD panel can be improved,        for example, imaging sticking is reduced.    -   2. According to an embodiment of the present invention, liquid        crystal polymer layers are further formed on the aligned        surfaces of the substrates to serve as alignment assistant        layers after performing alignment processes to the substrates.        Even the alignment processes performed previously are        non-contact alignment processes, the alignment anchoring energy,        and further the display quality of the LCD panel, can still be        improved greatly due to the alignment assistance function of the        liquid crystal polymer layers.    -   3. The present invention may also be applied to an existing LCD        panel having alignment material layers therein, that is, liquid        crystal polymer layers are further formed on the aligned        alignment material to serve as alignment assistant layer after        alignment processes have been performed to the alignment        material. Due to the alignment assistance function of the liquid        crystal polymer layers, the problem of insufficient anchoring        energy caused when conventional non-contact alignment processes        are performed can be resolved.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1. A liquid crystal display (LCD) panel, comprising: a first substrateand a second substrate; at least one liquid crystal polymer layer,disposed on the surface of at least one of the first and the secondsubstrate; a liquid crystal layer, disposed between the first and thesecond substrate.
 2. The LCD panel as claimed in claim 1, wherein thesurfaces of the first and the second substrate are comprised of aconductive layer or an insulating layer.
 3. The LCD panel as claimed inclaim 1, wherein the first substrate is an active device array substrateor a passive matrix substrate, and the second substrate is a colorfilter substrate or a counter electrode substrate.
 4. The LCD panel asclaimed in claim 1 further comprising at least one alignment layerdisposed between the surface of the first substrate and the liquidcrystal polymer layer and/or between the surface of the second substrateand the liquid crystal polymer layer.
 5. The LCD panel as claimed inclaim 4, wherein the material of the alignment layer comprises polyvinyl alcohol, polyimide, polyamic acid, azo-benzene, poly vinylcinnamate, compound containing coumarin group, compound containingchalcone groups, or polyamic acid.
 6. The LCD panel as claimed in claim4, wherein the material of the alignment layer comprises diamond-likecarbon, SiO_(x), or SiN_(x).
 7. The LCD panel as claimed in claim 4,wherein the alignment layer is a multi-domain alignment layer.
 8. Afabricating method of a LCD panel, comprising: providing a firstsubstrate and a second substrate; forming a liquid crystal monomer layeron the surface of at least one of the first and the second substrate;performing a curing step to the liquid crystal monomer layer to induce apolymerization reaction, so as to form a liquid crystal polymer layer;and assembling the first and the second substrate and filling a liquidcrystal layer between the first and the second substrate.
 9. Thefabricating method as claimed in claim 8, wherein the surfaces of thefirst and the second substrate are comprised of a conductive layer or aninsulating layer.
 10. The fabricating method as claimed in claim 8,wherein the curing step comprises an illuminating step or a heatingstep.
 11. The fabricating method as claimed in claim 8, wherein thefirst substrate is an active device array substrate or a passive matrixsubstrate, and the second substrate is a color filter substrate or acounter electrode substrate.
 12. The fabricating method as claimed inclaim 8 further comprising performing an alignment process to thesurface of at least one of the first and the second substrate beforeforming the liquid crystal monomer layer on the surface of at least oneof the first and the second substrate.
 13. The fabricating method asclaimed in claim 12, wherein the alignment process comprises a particlebeam alignment process, a photo alignment process, or a contactalignment process.
 14. The fabricating method as claimed in claim 12,wherein the alignment process is a multi-domain alignment process. 15.The fabricating method as claimed in claim 14, wherein the multi-domainalignment process is performed along with at least one of the particlebeam alignment process, the photo alignment process and the contactalignment process.
 16. The fabricating method as claimed in claim 8further comprising forming an alignment layer on the surface of at leastone of the first and the second substrate before forming the liquidcrystal monomer layer.
 17. The fabricating method as claimed in claim16, wherein the material of the alignment layer comprises poly vinylalcohol, polyimide, polyamic acid, azo-benzene, poly vinyl cinnamate,compound containing coumarin group, compound containing chalcone groups,or polyamic acid.
 18. The fabricating method as claimed in claim 16,wherein the material of the alignment layer comprises diamond-likecarbon, SiOx, or SiNx.
 19. The fabricating method as claimed in claim 16further comprising performing a alignment process to the alignment layerafter forming the alignment layer on the surface of at least one of thefirst and the second substrate.
 20. The fabricating method as claimed inclaim 19, wherein the alignment process comprises a particle beamalignment process, a photo alignment process, or a contact alignmentprocess.
 21. The fabricating method as claimed in claim 19, wherein thealignment process is a multi-domain alignment process.
 22. Thefabricating method as claimed in claim 21, wherein the multi-domainalignment process may be performed along with at least one of theparticle beam alignment process, the photo alignment process and thecontact alignment process.